Non-woven webs of fabric having variable thickness are known in the art, as shown for instance in U.S. Pat. No. 3,402,227, dated Sept. 17, 1968. Also the use of non-woven fabric on earthern surfaces to spread the stress from a roadway or a railway communication route over wider areas, are known in the art, with such fabric being formed for instance of non-woven polyester, and having the ability to filter out fine soil particles that would or could otherwise contaminate the roadway support bed or the railroad track support bed, and also possessing the capability of passing water through the mat so as to actually to aid in drainage of water from the soil beneath the mat. U.S. Pat. No. 3,670,506, dated June 20, 1972, entitled "Process for Stabilizing Soils" is directed to a method of utilizing non-woven fabric in poor support areas.
Also the use of mats for protecting bridge decks in a railroad environment are known such as for instance from U.S. Pat. No. 3,587,964, dated June 28, 1971.
However, to applicants' knowledge, these prior art mats in a roadway or railroad environment were of generally uniform thickness throughout. Such prior art mats are generally one unitary member formed of predetermined uniform thickness of fabric material and cut into predetermined lengths for use at the site of use.
Moreover, in applicant Marsh's pending U.S. patent application, Ser. No. 134,787, filed Mar. 28, 1980, now U.S. Pat. No. 4,311,273, and entitled "Variable Thickness Fabric Mat for Railway Track Structure and Method" and applicant Luebke's U.S. patent application, Ser. No. 92,709, filed Nov. 9, 1979, now U.S. Pat. No. 4,265,398, and entitled "Variable Thickness Mat for Stress Transition Zones of Railway Track Crossings Switches and the Like and Method of Use", there are disclosed various configurations of fabric mat for use in the environmental areas specified.